Field of the Invention
The present invention generally relates to suspension systems for wheeled vehicles and trailers, and more particularly to energy storing suspension components having locating and retention features within an axle coupling assembly. This disclosure presents several example embodiments that are representative of energy storing suspension components that may be utilized for particular purposes.
Discussion of the Prior Art
Wheeled vehicles and trailers commonly have suspension systems that utilize energy storing suspension components, such as spring members in the form of a leaf spring, or support members in the form of a trailing arm or support beam, and the like, in suspending a vehicle or trailer frame and/or body assembly above an axle to which wheels are rotatably connected. The suspension system of a vehicle generally may be referred to as the unsprung portion of the vehicle, while the frame and/or body that is carried by the suspension may generally be referred to as the sprung portion of the vehicle. Within the suspension system, the energy storing suspension components are connected to the axle via axle coupling assemblies. For ease of reference, the suspension systems may be said to be a part of a chassis of a wheeled vehicle or trailer, with an understanding that the chassis may include a frame assembly or may be integrally constructed with a body assembly, such as in a so-called unibody construction.
Suspension systems typically include active suspension components designed to isolate from the sprung portion the disturbances encountered by the unsprung portions, such as occur during acceleration and deceleration, or during jounce and rebound of the axle when traversing bumps in a road surface and the like, and to withstand lateral and roll forces, such as are encountered when cornering. Over time, a variety of different suspension components and entire suspension systems have been developed to alter the capacity, ride height, ride comfort, handling characteristics and durability of vehicles and trailers. The desire to alter these features with respect to suspensions may be prompted by a variety factors. However, suspension components, such as energy storing suspension components in the form of spring members, support members, and the like, play a dynamic role within suspension systems and their spring rates, both vertically and laterally, as well as stress levels and the ability to transfer loads to adjacent structures, present complex challenges.
For instance, a vehicle may utilize a traditional leaf spring member that may be relatively thicker in an axle seat portion where the axle is coupled to the spring member within an axle coupling assembly. It is fairly common for a spring member to include an aperture through the center of the spring within the axle seat portion to receive a fastener therethrough, such as a bolt, to assist in holding the spring laterally and longitudinally with respect to the other suspension components for mounting in an axle coupling assembly. This can be helpful during assembly, but unfortunately once the fasteners for the axle coupling assembly are installed and the suspension components are clamped together, it also can cause localization of stresses through the weakened center portion of the spring member having the aperture. This can result in increased likelihood of spring member fracture, due to the localized stresses and potentially an increased likelihood of hydrogen assisted cracking, which may otherwise be referred to as hydrogen embrittlement failure.
In assemblies that include two or more leaf spring components, the outer suspension component may include an end formed with a “military wrap”, which encircles the eye of the leaf spring that is mounted to a frame member and provides a redundant feature to retain the leaf spring in the event of a fracture. However, suspensions having a single leaf spring lack such a redundant retention feature. Therefore, if a spring member has fractured within the axle coupling assembly, the opposed portions of the axle seat portion of the spring member and the associated opposed limbs of the spring member, for instance a front limb and rear limb that extend from the axle seat portion, will have a tendency to work their way out of the clamping region of the axle coupling assembly. If one of the fractured portions of the spring member disengages from the axle coupling assembly, the remaining suspension components within the axle coupling assembly likely will permit relative angular movement therebetween, tending to remove the compression within the axle coupling assembly and resulting in further breakdown of the clamping capability of the axle coupling assembly. The loss of clamp load also may permit the axle to shift, resulting in axle misalignment.
Such disengagement of one or more of the fractured portions of a spring member can compromise the integrity of the suspension system and ultimately the handling and safety of the vehicle. Moreover, a fractured spring results in vehicle downtime and costs associated with suspension system repairs. Thus, beyond the potential concerns for safety, spring fracture and disengagement can give rise to concerns relating to a lack of productivity, and to costly and time consuming repairs.
In addition, such a spring member typically will have an axle seat portion having a width and thickness configuration that is intended to be sufficient to withstand concentrated levels of stress in the area of the aperture. Unfortunately, such a configuration may include increased thickness and width of the spring member to be able to overcome the stress concentration that is due to having an aperture through the center of the spring. If an increase in thickness or width is needed, it would result in added mass. Added unsprung mass not only reduces vehicle fuel economy, but also requires greater power to accelerate the vehicle, greater breaking capacity to stop the vehicle, and undesirable ride characteristics.
Some prior art devices have included relatively deep depressions in one surface of a spring member, with the depressions extending through the spring member and producing corresponding projections outward from an opposed surface. Such depressions can require a large amount of energy to form, but also tend to result in weakened areas that are susceptible to localized stresses and shearing due to the thin material cross-sections in the effective sidewalls of the depressions. Thus, the depressions may have been added for locating purposes, but in turn, may lead to further disadvantages relating to potential stress concentration and fracture within the prior art suspension systems.
The present disclosure addresses shortcomings found in prior art suspension systems for wheeled vehicles and trailers and in energy storing suspension components utilized therein.